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373
METALLUHGY OP IRON AND STEEL.
TABLE XVII-0.
Combination, of Data in Table XVII-N" to Obtain the Lines in
Fig. XVII-A.
Class.	Carbon ; per cent.	Phosphorus ; per cent.	Manganese ; per cent.	Ultimate strength; Ibs. per sq.. inch.
	.1520	.0565	.440	61806
	.1713	.0570	.453	63637
	.2486	.0537	.497	72185
Line AA.	.3268	.0480	.529	80626
Acid, steel.	.3609	.0443	.628	83886
	.3943	.0419	.526	87155
	.4357	.0384	.519	91278
	.4693	.0371	.518	95052
	.5130	.0358	.513	99795
	.0978	.0094	.366	50834
	.1639	.0107	.450	57001
Line BB. Basic steel.	.2115 .2403 .2681	.0113 .0110 .0109	.465 .471 .470	61502 64086 66297
	.3081	.0108	.466	69626
	.3582	.0113	.469	74203
the groups of low-carbon steel, and hence the line will give a provisional value of carbon. The general trend is determined by stretching a thread along its length and noting the tangent made with the horizontal. In this way the line AA indicates a value for carbon of about 1050 pounds for each 0.01 per cent.; allowances have yet to be made for the effect of phosphorus and manganese, but this figure serves as a working basis for similar provisional estimations of the other elements. In explaining the method used to determine the value of phosphorus and manganese, no mention will be made of these provisional values, the figures given being in each case the final results.
THE EFFECT OF PHOSPHORUS ON ACID STEEL.
The study into the effect of phosphorus will be confined to acid steel, for in the basic steels under consideration the proportion of phosphorus was so. low that the differences were almost within the limits of error. The bars were classified according to carbon arid each of these main groups was then sub-divided according to phosphorus. Heats with 0.03 per cent, of phosphorus constituted one group; those with 0.031 per cent, another; those with 0.032 per cent, another, and so on. These groups were put together so as to give four or five points with an equal number of heats in each, the re-